Eni Oko, Meihong Wang* and Colin Ramshaw

Dynamic Modelling, Validation and Analysis of Rotating Packed Bed Absorber for Post-Combustion Carbon Capture Based on Chemical

Absorption

Process/Energy Systems Research Group, School of Engineering, University of Hull, HU6 7RX, UK

Abstract for oral presentation

Conventional absorbers used in post-combustion carbon capture processes are large in size, contributing significantly to plant footprint andcapital cost.For instance, post-combustion capture process for capturing CO2 from a 500 MWe coal-fired subcritical power plant will involve absorber columns with diameter of about 25 m and height over 27 m.Through process intensification (PI), the size of this equipment can be reduced significantly. Rotating packed bed (RPB), a typical PI equipment, has been used to demonstrate that about 12 times reduction in the absorber size was possible (Joel et al., 2014). RPB was originally proposed by Ramshaw and Mallinson (1981) and meaningful studies of its steady state characteristics have been reported. There is no report yet on the dynamic characteristics of RPB absorbers.

In this study, a rate-based dynamic model of an RPB for post-combustion carbon capture from power plant flue gas using monoethanolamine (MEA) solution as solvent is developed using gPROMS ModelBuilder®. Thermo-physical properties of the CO2-MEA-H2O system were based on eNRTL in Aspen Plus® accessed via CAPE-OPEN interface from gPROMS ModelBuilder®. Default parameters of eNRTL in Aspen Plus® were updated through regression of VLE data of the system since high concentration of MEA is used. Steady state and dynamic validations of the model were performed, the results of which showed good agreement for steady state and dynamic scenario.

The model has been used to carry out different process analysis, namely impact of concentration of MEA solution, rotating speed of the RPB among others. From the results, it is found that improvement in CO2 capture level is not very significant beyond 75 wt%MEA concentration. Also, dynamic behavior of the RPB was investigated through application of different levels of step changes in the inlet flue gas flowrate to determine the process dynamics (e.g. time constant) among others.

Keywords: Process modelling and simulation, Process intensification, Rotating packed bed, Post-combustion CO2 capture, Chemical absorption

Acknowledgement: The authors are grateful to the Engineering and Physical Sciences Research Council (EPSRC)(Ref: EP/M001458/1) and EU IRSES (Ref: PIRSES-GA-2013-612230) for financial support.

References: Ramshaw, C., Mallinson, R.H., 1981. Mass transfer process. US Patent 4283255. Joel, A.S., Wang, M., Ramshaw, C. and Oko, E. Process analysis of intensified absorber for post-combustion CO2capture through modelling and simulation. International Journal of Greenhouse Gas Control21 (2014), 91-100

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